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What methods can interface have in Java?
The interface in Java is a mechanism to achieve abstraction. There can be only abstract methods in the Java interface, not method body. It is used to achieve abstraction and multiple inheritance in Java. In other words, you can say that interfaces can have abstract methods and variables.
How can we avoid implementing all methods interface in Java?
Use abstract class instead of interface….In this abstract class,
- Methods which are optional for Child class – provide implementation in your abstract class.
- Methods which are mandatory for Child class – declare as abstract in your abstract class, child class must provide implementation.
How are interfaces used in a Java program?
An interface can extends another interface or interfaces (more than one interface) . A class that implements interface must implements all the methods in interface. All the methods are public and abstract. And all the fields are public, static, and final. It is used to achieve multiple inheritance. It is used to achieve loose coupling.
Can a class extend another interface in Java?
An interface can extends another interface or interfaces (more than one interface) . A class that implements interface must implements all the methods in interface. All the methods are public and abstract. And all the fields are public, static, and final.
How are interface fields public and abstract in Java?
In other words, Interface fields are public, static and final by default, and the methods are public and abstract. As shown in the figure given below, a class extends another class, an interface extends another interface, but a class implements an interface.
Do you have to declare interface as public in Java?
5) Class that implements any interface must implement all the methods of that interface, else the class should be declared abstract. 6) Interface cannot be declared as private, protected or transient. 7) All the interface methods are by default abstract and public.